Chlorine-containing resins such as vinyl chloride resins are used in a variety of applications because, for example, they have superior flame retardancy and chemical resistance. However, chlorine-containing resins have a drawback in that, in thermal processing or the like, a part of the carbon-chlorine bond is thermally broken to cause dehydrochlorination which results in a reduced mechanical strength and occurrence of coloring, thereby impairing the marketability of the resin.
In order to solve the above-described drawback, a variety of stabilizers have been developed, and thereamong, particularly, mixtures and the like of a lead or cadmium compound and a barium compound have been known to have superior stabilizing effect. However, in recent years, the trend is toward restricting the use of lead compounds and cadmium compounds from the safety standpoint, so that such stabilizers using a lead or cadmium compound are now being replaced by those in which a highly safe zinc compound is used in combination with an organic acid salt of alkaline earth metal or an inorganic compound such as hydrotalcite or zeolite.
Since these low toxic stabilizers by themselves cannot provide sufficient stabilizing effect, in order to improve the resistance to light, heat, oxidation and the like, a variety of additives, such as organic phosphite compounds, epoxy compounds, phenol-based antioxidants, benzophenone-based or benzotriazole-based ultraviolet absorbers and hindered amine-based light stabilizers, are used in combination.
However, it is still difficult to attain sufficient improvement in the heat resistance even with the use of these non-metallic stabilizing aids in combination, and there is also a room for improvement in terms of the processability of resin compositions.
Patent Document 1 discloses a vinyl chloride resin composition in which a polyester-based plasticizer, a non-ionic surfactant and a polymer of alkyl ester of acrylic acid or methacrylic acid, the polymer having a number average polymerization degree of 50, are added to a vinyl chloride resin.